The present invention is directed to integrated circuits and their processing for the manufacture of semiconductor devices. More particularly, the invention provides a method and a device for an etching process using an etch stop region for the manufacture of integrated circuits. Merely by way of example, the invention has been applied to the chemical dry etching process for the manufacture of integrated circuits. But it would be recognized that the invention has a much broader range of applicability.
Integrated circuits or “ICs” have evolved from a handful of interconnected devices fabricated on a single chip of silicon to millions of devices. Current ICs provide performance and complexity far beyond what was originally imagined. In order to achieve improvements in complexity and circuit density (i.e., the number of devices capable of being packed onto a given chip area), the size of the smallest device feature, also known as the device “geometry”, has become smaller with each generation of ICs. Semiconductor devices are now being fabricated with features less than a quarter of a micron across.
Increasing circuit density has not only improved the complexity and performance of ICs but has also provided lower cost parts to the consumer. An IC fabrication facility can cost hundreds of millions, or even billions, of dollars. Each fabrication facility will have a certain throughput of wafers, and each wafer will have a certain number of ICs on it. Therefore, by making the individual devices of an IC smaller, more devices may be fabricated on each wafer, thus increasing the output of the fabrication facility. Making devices smaller is very challenging, as each process used in IC fabrication has a limit. That is to say, a given process typically only works down to a certain feature size, and then either the process or the device layout needs to be changed. An example of such a limit is chemical dry etching process used for the manufacture of integrated circuits in a cost effective and efficient way.
Etching is an important process in semiconductor manufacturing. Etching involves removing selected regions from the surface of a wafer using a plasma process that may include a physical process, chemical process, or the combination thereof. Usually a goal of etching is to faithfully reproduce masking patterns. To achieve this goal, it is often desirable to for the etching process to be highly selective both in patterns and depth, which is often achieve through chemical dry etching.
Chemical drying etching usually involves generating reactive species in plasma, providing these species to the surface of material being etched, species being absorbed, reacting of these species on the surface to form volatile by-product, absorbing or the by-product by the surface, and diffusing of the desorbed species diffusing into gas. There are many various dry-etch systems to accomplish these steps. For example, dry-etch systems include barrel etchers, downstream etchers, parallel-electrode (planar) reactor etchers, stacked parallel-electrode etchers, hexode batch etchers, magnetron ion etchers, etc.
Regardless of type of dry-etch systems being used, an aspect for an etching process is a highly selective etching depth. There are various methods for controlling the etch depth. For example, a layer of “etch stop” may be used during the etching process to control etching depth. An etch stop layer is usually consisted of materials that feature drastically different etch characteristics from the material to be etched. The etch stop layer is generally placed underneath the etched material to stop etching process.
Although the use of etch stop layers is fairly common, there are many limitations. As an example, etch stop layers are often difficult to form for providing selectivity between materials that may have common characteristics. That is, it is often difficult to selectively remove different dielectric materials from each other. Depending upon application, convention etching process utilizing an etch stop layer may adversely affect the characteristics of the wafer being etched.
Therefore, it is desirable to have an improved system and method for etching.